Antenna



NOV- 30, 1948 L. BUCHWALTER Erm. 2,455,224 f ANTENNA Filed June 16. 1944 y :Nvu/1% ou/SE eucHwAL A GEORGE @HARVEY Non. E@ i943 rattan ANTENNA Louise Buchwalter,

G. Harvey,

Hallsville, h10, and George Boston, Mass., assignors, by mesne assignments, to the United States of America as represented by the Secretary of War y Application June 16, 1944, Serial No. 540.571

This invention relates to an antenna and more particularly to a radiating array type antenna adapted for use with a high frequency communication system. This antenna, when disposed in its contemplated vertical position, radiates vertically polarized electromagnetic waves in a distribution pattern that is substantially uniform in azimuth and relatively narrow in elevation. Such a radiator will have particular application to radio systems wherein a uniform azimuth characteristic is desirable.

The principal object of the invention is to provide a simple and inexpensive radiating antenna having the above type radiation pattern together with Va. satisfactory gain characteristic. Other objects relate to the use of insulation material inV the antenna structure whereby effective insula-1 tion is provided and whereby moisture is effectively excluded from the construction.

The present antenna is adapted principally for use at short Wave lengths of the order of centimeters. In general, the invention comprises a vertically disposed length of high frequency conductor, such as a coaxial cable or a hollow wave guide, wherein the outer conductor of such cable or wave guide length is made up ofa plurality of spaced individual metallic sections. In the case of a coaxial cable, a solid dielectric is provided between thecentral conductor and the outer conductor, the individual sections of the latter being carried thereby in spaced and aligned relation. Radiation of energy occurs from the regions or apertures between conductor sections, these regions being separated by a distance along the conductor corresponding'generally to the wave length of the energy within the conductor. Thus radiations from the several regions in directions normal to th axis of the conductor will be in phase. With the antenna disposed in a vertical position, the wave energy radiated therefrom will have a vertically polarized characteristic.

In the drawing, Fig. 1 is a side elevational view, partly in section, of the antenna construction; Fig. 2 is a. sectional view on the line 2-2 of Fig. 1; and Fig. 3 shows the energy distribution pattern of the antenna.

Referring now to Fig. 1, the invention is shown embodied in a coaxial Vcable type conductor.

although it is to be understood that the inventionA may be applied to a hollow wave guide type conductor, if desired. In the use of a wave guida,

care must betaken to insure excitation of" the guide in the appropriate mode of transmission, in this instance the mode corresponding tol that of the coaxial mode. The coaxial cable type 2 Claims. (Cl. Z50-33.53)

antenna has central conductor 5 adapted to be connected to the central conductor of an associated feeder. transmission line. Central conductor 5 has mounted thereon a plurality of dielectric sleeves 6. Any usual dielectric material, such as polystyrene, may be used for the sleeves, the coeiiicient of expansion of the dielectric being comparable to that of the metallic conductors for mechanical reasons. An integral annular flange 1 extends from the exterior surface of each sleeve 6, the width of flange 'l being generally small as compared to the axial length of the sleeve. Metallic outer conductor sections 8 are snugly carried on the outer surfaces of sleeves 6, annular anges 'l on the sleeves serving to space the ends ofadjacent conductor sections. The distance between adjacent section ends may be varied in accordance with impedance matching requirements.

As will be understood, the antenna array is assembled by alternately fitting dielectric sleeves 5 and outer conductor sections t to central conductor 5. The assembly thus comprises a coaxial cable l having a substantially continuous solid dielectric between inner and outer conductors (adjacent sleeves li are in abutting relation) with the outer conductor having spaced annular regions of discontinuity. Spacer iianges l lying in the regions of conductor discontinuity may be substantially ilush with the outer surface of the conductor sections. The axial length of dielectric sleeves G is generally equal to a wave length of the conducted wave energy. As ilanges 'l are uniformly positioned on the respective sleeves S, the distance lbetween corresponding points on two adjacent flanges likewise corresponds generally to a wave length. y

Thus, it will be seen that radiations emanating from the several annular regions of discontinuity y in the outer conductor will be in phase, and therefore that successive radiations will combine in space in an additive manner in a plane normal tothe axis of `the antenna. At elevation angles above and below such plane, there is interference between radiations from the various regions oi.' conductor discontinuity, the interference increasing with the angle of elevation. Beyond a certain critical vertical angle, radiation is substantially zero due to increased interference. The array is terminated in any suitable manner-as in a short circuit provided by metallic end disc 9.

The invention rmay be applied to a hollow wave guide type conductor in substantially the same "l manner as described above. In this case the wave guide is fed in a mode of transmission corresponding to the normal coaxial mode.

As will be understood, the antenna array is normally disposed in a vertical position. The energy distribution pattern shown in Fig. 3 is a sectional view on a vertical plane passing through the array. The pattern is substantially circular in a horizontal plane passing through the antenna (in azimuth), and, as shown, it is relatively narrow in the vertical aspect. The precise width of the vertical beam will depend, of course, upon the number of annular radiating apertures provided.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:

1. An antenna array comprising a coaxial cable adapted to be fed with high frequency electromagnetic waves, said cable having an inner con- .ductor and a spaced outer conductor, a dielectric therefrom are in phase.

2. -An antenna array adapted to lbe fed with high frequency electromagnetic waves, said array comprising a central conductor, a plurality of dielectric sleeves mounted on said conductor in abutting relation with the conductor passing through the center cf said sleeves, an integral annular flange on the exterior surface of each of said sleeves, said anges being uniformly positioned on said sleeves, anda plurality of metallic sections of outer conductor mounted in spaced and aligned relation on said sleeves, said flanges cooperating to space the ends of adjacent outer conductor sections, corresponding points on adjacentl flanges being spaced a distance equal to one Wave length whereby radiations from the regions between outer conductor sections are in phase.

LOUISE BUCHWALTER.

GEORGE G. HARVEY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Dallenbach May 30, 

